Unloaders for refrigerant compressors



Jan. 12, 1960 A COURTNEY, JR 2,920,812

UNLOADERS FOR REFRIGERANT COMPRESSORS Filed Dec. 19, 1956 R TIMER l 21 Wi! PRESSURE COMPRESSOR l DISCHARGE -7 TUBE 0| PUMP CONDENSERInventoriuia fufl Wlbuflfneg,Jn

UNLOADERS FOR REFRIGERANT COMPRESSORS I Arthur W. Courtney, Jr.,Grottoes, Va., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania "Application December 19,1956, Serial No. 629,266

4 Claims. .(Cl. 230-7) 1 This invention relates to refrigerantcompression, and

has as an object to improve the mechanisms used for unloading suchcompressors.

In many refrigerant compressors, unloading mechanisms are used forreducing the starting power, and for reducing the output as loadreductions take place.

The E. R. Wolfert Patent No. 2,296,304 discloses a successful form ofunloader in which unloading is accomplished by depressing suction valvereeds so that they do not act as check valves as they ordinarily doduring the compression strokes of the pistons in their respectivecylinders. A toothed bar called a comb is usedto hold a set of suctionreeds down, this comb being forced down by refrigerant discharge gaspressure acting on a piston in an unloader cylinder located over thecomb. The comb is returned from the depressed (unloading) position byrelieving the pressure in the unloader cylinder and allowing return.springs and the spring action of the reeds to lift the comb to itsneutral position.

Lubricating oil is recirculated with the refrigerant through arefrigeration system, and is used in some compressors for providingunloading pressure. It has the advantage that it is incompressible, buthas the disadvantage that sufiicient oil pressure for unloading is notavailable immediately on the start of a compressor.

, This invention provides for starting the unloading of a compressorcylinder with discharge gas pressure, and,

embodiment of this invention.

, A conventional refrigerant compressor 10 driven by anelectric motor11, has three pairs of cylinders. C1, C2 and C3,-with their associatedcylinder heads H1, H2 and H3 respectively. Each cylinder head would havethe unloader cylinder 12, although for simplicity of illustration andexplanation the head H1 only is shown with unloader cylinders. Theunloader cylinder 12 would contain pistons which would depress combs todepress suction reed valves for unloading as is conventional.

The compressor 10 would be connected by a gas discharge tube 13 to aconventional water-cooled condenser 14 which would be connected througha tube 15 and a conventional expansion valve 16 to a conventionalevaporator 17, the outlet side of which is connected by a tube 18 to thesuction side of the compressor.

The discharge tube 13 is connected through a tube 19, a three-way valveC, a tube 21 and valve B to the inlets of the unloader cylinders 12. Thevalve C is connected through a tube 23 to the suction side of thecompressor 10. The valve C is adapted to be adjusted by a solenoid 24 toconnect the tube 21 to the tube 19 or to the tube 23. The valve B isadapted to be opened and closed by a solenoid 26. A tube 27 connects theoil pump of the United States Patent 0 duced at any time into them.

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2 compressor through valve A and check valve 28 to the inlets of thecylinders 12. A solenoid 29 opens and closes the valve A.

The solenoids 24 and 26 are connected directly to supply line L2. Thesolenoid 26 is connected through contact 30 and armature 31 of relay 32and L1 when the relay 32 is energized. The solenoid 24 is connectedthrough contact 35 and armature 31 of the relay 32 when the relay 32 isenergized.

The solenoid 29 is connected directly to the line L2, and through downcontact 36 of switch 33 when the switch is on the contact 36, andcontact 34 and armature 31 of the relay 32 when the relay isdeenergized.

The solenoid 26 is also adapted to. be connected through the up contact37 of the switch 33, when the switch is on contact 37, relay contact 34,and relay armature 31, to L1 when the relay is deenergized. V

The energizing winding of the relay 32 is connected through a timer 38to the supply lines L1 and L2 which would be connected to the startercircuit of the compressor motor.11 so as to be energized when thecompressor is started.

Operation 7 At the start of operation, the relay 32 would be energizedthrough the timer 38, and would pull up its armature 31 against thecontacts 30 and 35,- closing the energizing circuits of the solenoids 24and 26. The solenoid 24 would then adjust the valve C to connect thetube 21 to the tube 19. The solenoid 26 would open the valve B,admitting discharge gas supplied through the tube 19, the valve C, thetube 21 and the valve B, into the unloader cylinder 12. r

The solenoid 29 is deenergized at this time, and its valve A is closed,preventing oil from the tube 27 from being supplied into the unloadercylinders 12.

The discharge gas pressure builds up rapidly immediately after starting,and causes the unloader cylinders 12 to unload their associatedcompressor cylinders.

At the end of about 10 to 15 seconds after the start, the timer 38 timesout, deenergizing the relay 32. Its armature 31 then leaves the contacts30 and 35 opening the previously described energizing circuits of thesolenoids 24 and 26. The valve C, as a result of the deenergization ofthe solenoid 24, disconnects the tube 21 from the tube 19, and connectsthe tube 21 to tube 23. The valve B as a result of the deenergization ofthe solenoid 26 closes.

At the same time the relay armature 31 touches the relay contact 34connecting the solenoid 29 to the supply lines so that the solenoid 29is energized and opens the valve A, .supplying oil through the valve Aand check valve 28 into the unloader cylinders 12 for unloading thecompressor. The valve B is closed at this time so that there is norelief of this pressure.

Thereafter until the compressor is stopped, unloading is controlled bythe switch 33. When this switch is placed on the down contact 36 by anoperator or under thermostatic control as described in said Wolfertpatent, unloading is accomplished. When loading is required the switch33 is placed against its up contact 37. The switch in leaving its downcontact 36 deenergizes the solenoid 29 causing the valve A to close.

The switch 33 on touching its up contact 37 energizes the solenoid 26causing it to open the valve B, connecting the unloader cylinders 12through the valves B and C, and tube 2 3 to the suction pressurepermitting the relief of the oil pressure which previously causedunloading.

The oil filling of the unloader supply lines through valve A is notdisturbed since no discharge gas is intro- Norrnal operation on oil thusis not hamperedas it is when discharge gas is introduced into the supplylines. g o

While the oil pressure available in a refrigerant compressor is not asgreat as is the discharge gas pressure, byusing the check valve 28, theoil pressure is sufficilent The suction valve reeds willbe opened duringevery compressor cylinder intake stroke. All that is really required ofan unloader is sufficient force to make theiunload er combs follow inthe path of the suction valve reeds during their opening. However, in arelativelyiinelastic system, in this case an oil filled system, the useof a check valve will prevent any return travel even though the supplypressure to the unloader cylinder is relatively low. The check valvemakes the system irreversible except when the valve 3 is opened torelieve theuoil pressure when loading. As in the case of systems usingdischarge gas pressure, the spring loading and valve, reed tension willreturn the unloader assembly to sienna position.

I claim as my invention: a I

1. In an unloader for a cylinder of a. refrigerant compressor, saidcylinder: having an unloader cylinder for opening the suction valvemeans of said compressor cylinder whenfluid is supplied into saidunloader cylinder, the improvement comprising a gas control valveconnected to said unloader cylinder, an oilcontrol valve connected tosaid unloader cylinder, a three-way valve connected to said gas controlvalve, gas tubing connecting said three-way valve to the discharge gasside of said compressor, v suction tubing connecting'said three-wayvalve to the suction side of said compressor, oil tubing connecting,said oil control valve to the oil supply of said compressor, meansincluding control means connected to said gas and oil control valves andto said three-way valve for closing said oil control valve, for openingsaidgas control valve, and for adjusting said three-way valve to connectsaid gas control valve to said gas tubing and to disconnect said gascontrol valve from said suction tubing, whereby discharge gas issupplied through said gas tubing, said three-way valve and said gascontrol valve into said unloader cylinder, means in eluding said controlmeans for closing said gas control valve, for opening said oil controlvalve, and for adjusting said three-Wayvalve to connect said gas controlvalve to said suction tubing and to disconnect said gas control valvefrom said gas tubing, whereby oil is supplied through said oil tubingand said oil control valve into said unloader cylinder, and wherebysuction is applied through said suction tubing, said three-way.valve andsaid gas control valve to said unloader cylinder when said oil controlvalve is next closed and said gas control valve is next opened, torelieve the oil pressure within said unloader cylinder, and meansincluding said control means for closing said oil control valve andopening said gas control valve.

2. The invention claimed in claim 1 in which a check valve is providedand connected between said oil con- 2,920,812 p a e 4 t trol valve and'said unloader cylinderf'said check valve permitting the flowof oil tosaid unloader cylinder when said oil control valve is open, andpreventing the How of discharge gas into said oil control valve duringthe discharge strokes of said compressor cylinder.

3. In an unloader for a cylinder of a refrigerant compressor, saidcylinder having an unloader cylinder for opening the suction valve meansof said compressor cylinder when fluid is supplied into said unloadercylinder, the improvement comprising a gas control valve connected tosaid unloader cylinder, a gas control solenoid for opening and closingsaid gas control valve connected to said gas control valve, an oilcontrol valve connected to said unloader cylinder, an oil controlsolenoid for opening and closing said oil control valve connected tosaid oil control valve, a three-way valve connected to said gas controlvalve, gas tubing connecting said three-way valve with the discharge gasside of said ;;compr essor suction tubingconnecting said three-way valvewith the suction side .ofsaid compressor, a third solenoid for adjustingsaid threeeway valve to connect said gas control valve to said gastubing or to said suction tubing, connected to said three-way valve,means including a relay adapted to be energized when said compressor isstarted, and a first switch which is closed when said relay is,energized, for energizing said gas control solenoid to open said gascontrol valve and for energizing 'said third solenoid to adjust saidthree-Way valve to connect said gas control valve to said gas tubing,timing means connected to said relay for deenergizing said relay apredetermined time interval after said relay is energized, said relayhaving a second switch which is closed when said relay is deenergized,means including said second switch for energizing said oil controlsolenoid to open said oil control valve, and means including aloader-unloaderv switch .connectedto said oil control solenoid fordeenergizing and energizing said oil control solenoid to close and openrespectively, said oil control valve, and connected to said gas controlvalve solenoid for energizing and deenergizing said gas control solenoidto open and close respectively, said gas controlvalve.

4. The invention claimed in claim 3 in which a check valve is providedand connected between said oil control valve and said unloader cylinder,said check valve perrnitting the flow of oil to said unloader cylinderwhen said oil control valve is open, and preventing the flow ofdischarge gas into said oil control valve during the discharge strokesof said compressor cylinder.

References Cited in the file of this patent I UNITED STATES PATENTS,2,389,348

